Add zstd.

3rdparty/zstd-1.5.0/contrib/largeNbDicts/README.md

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+largeNbDicts
+=====================
+
+`largeNbDicts` is a benchmark test tool
+dedicated to the specific scenario of
+dictionary decompression using a very large number of dictionaries.
+When dictionaries are constantly changing, they are always "cold",
+suffering from increased latency due to cache misses.
+
+The tool is created in a bid to investigate performance for this scenario,
+and experiment mitigation techniques.
+
+Command line :
+```
+largeNbDicts [Options] filename(s)
+
+Options :
+-r           : recursively load all files in subdirectories (default: off)
+-B#          : split input into blocks of size # (default: no split)
+-#           : use compression level # (default: 3)
+-D #         : use # as a dictionary (default: create one)
+-i#          : nb benchmark rounds (default: 6)
+--nbDicts=#  : set nb of dictionaries to # (default: one per block)
+-h           : help (this text)
+```